Method of producing fine tungsten powder from tungsten oxides

Abstract

The present invention relates to an improvement in the method and the apparatus for reducing tungsten oxide powder to tungsten metal powder. The method produces more uniform particle size distribution by decreasing the variability of temperature and inconsistency of reductant gas flow during the reduction process. The method includes the steps of: providing powder particles of WO x in a unique reaction boat with a low aspect ratio to a multi-tube furnace; (a) contacting particles of WO x , wherein x is at least 2.5, with hydrogen and water vapor under fluid bed conditions at a temperature in the range of about 600 degrees to about 1000 degree Centigrade and at a water partial pressure equal to or greater than the equilibrium partial pressure, whereby said particles of WO x are reduced essentially to particles of WO 2 with substantially no formation of tungsten metal, and (b) reducing the partial pressure of water in the fluid bed to a level sufficient to achieve reduction of said particles of WO 2 to tungsten metal while continuing to maintain said bed at a temperature which is substantially equal to or higher than said first temperature but not over about 1000 degree Centigrade.

What is claimed is:  
     
         1 . Apparatus for the production of tungsten metal powder using a push through furnace comprising: 
 rectangular reaction vessels with two sidewall, a front wall, a rear wall, and a bottom forming a cavity, and with a length width and height, and the ratio of said width to height is at least 8; and    said cavity is shaped to allow a stream of reductant gas to flow over and through tungsten oxide that was therein placed.    
     
     
         2 . The apparatus for the production of tungsten metal powder of  claim 1 , wherein said bottom of said reaction vessel is between 0.5 mm and 4 mm thick.  
     
     
         3 . The apparatus for the production of tungsten metal powder of  claim 1 , wherein said bottom of said reaction vessel is 2 mm thick.  
     
     
         4 . The apparatus for the production of tungsten metal powder of  claim 1 , further comprising a reaction vessel for holding the tungsten oxide, and a support portion, below said reaction vessel for contacting the furnace surface.  
     
     
         5 . The apparatus for the production of tungsten metal powder of  claim 4  wherein said support section is formed in a honeycomb configuration.  
     
     
         6 . The apparatus for the production of tungsten metal powder of  claim 4  wherein said apparatus is cast in one piece.  
     
     
         7 . The apparatus for the production of tungsten metal powder of  claim 1  wherein said front and said rear walls further comprise an inner surface, wherein said inner surface is inclined at an angle to promote said stream of said reductant gas to flow over and through said tungsten oxide.  
     
     
         8 . The apparatus for the production of tungsten metal powder of  claim 7  wherein said angle of said inner surface is a 45°.  
     
     
         9 . A method of producing tungsten metal powder comprising the steps of: 
 providing powder particles of WO x  into a reaction boat with a low aspect ratio;    contracting said powder particles of WO x  wherein x is at least 2.5, with hydrogen gas and water vapor under fluid bed conditions at a temperature in the range of 600 degrees to 1000 degree Centigrade; and    reducing the partial pressure of water in the fluid bed to a level sufficient to achieve reduction of said particles of WO 2  to tungsten metal.    
     
     
         10 . The method of producing tungsten metal powder of  claim 9 , further comprising the step of continuing to maintain said bed at a temperature which is substantially equal to or higher than said first temperature but not over about 1100 degree Centigrade.  
     
     
         11 . The method of producing tungsten metal powder of  claim 10 , further comprising the step providing dry H 2  gas through multiple, cross-flow inducing, inlet and outlet ports of a muffle.  
     
     
         12 . A method of producing fine tungsten powder from tungsten oxide comprising the steps of: 
 providing a muffle furnace with rectangular cross section trays;    loading said trays with a thin layer of tungsten oxide;    reducing said tungsten oxide under a hydrogen atmosphere; and    producing said fine tungsten powder.    
     
     
         13 . The method of producing fine tungsten powder from tungsten oxide of  claim 12  wherein said thin layer of tungsten oxide is between 1 mm and 12 mm high.